Abstract

A SQUIDacoustomagnetic spectrometer is used to detect changes of magnetization of tantalum metal produced by a continuous wave composite resonator in an external magnetic field. Acoustic power variations produce temperature variations in the spectrum and thus cause changes in the Curie susceptibility of the paramagnetic impurities present in the sample. Swept frequency acoustic spectra of single‐crystal tantalum standing waveresonances at the normal mode frequencies (mechanical resonances) are studied at 4.2 K. Depending on the rate of frequency sweep through a mechanical resonance, the applied acoustic power, and the magnetic field, the observed structure at the mechanical resonance frequencies can be both above and below the baseline. The low‐frequency side of each structure has a Lorentz line shape and the high‐frequency side has an exponential decay that is explained by heat exchange between sample and surroundings. This interpretation allows these structures to be used in general in continuous wavevelocity of sound and ultrasonic attenuation studies while making use of the high sensitivity of the SQUIDacoustomagnetic spectrometer.